Recently, it has been considered to bond a film, on which printing is made by an ink jet printer, to various kinds of base materials and use it for outdoor signboards, indoor signboards, drop curtains, roll screens, blinds, curtains, shutters, wall coverings and the like.
Printing by an ink jet printer is made in a manner of directing a jet of ink through a nozzle at a film. When a solvent type ink is used for this printer, it dries early so that the nozzle is readily clogged up with the dry ink. Therefore, a water-base ink is generally used for the printer. The water-base ink includes pigment, dye or both of them as a colorant and includes a dispersing agent soluble in water. A target color is obtained by plural coats with water-base inks of four colors, i.e., blue, red, yellow and black. The film on which printing is to be made is selected, according to application purposes such as places to be used (for example, outdoor or indoor) and how the film is to be used (i.e., a method of bonding the film to the base material), from among a thermoplastic resin film such as a polyvinyl chloride resin film, a polypropylene resin film, a polyester resin film and an acrylic resin film, paper, cloth, tarpaulin and the like.
Japanese Patent Application Laid-Open Gazette No. 5-229246 discloses a technique in which an ink absorbing material layer is provided on a surface of a plastic base film in order to increase the definition of images by the ink jet printer and the absorbability to the water-base ink and the ink absorbing material layer is formed by coating the base film with a polyester resin dispersion in water. The coating liquid is obtained by modifying polyester resin with a compound having a polymeric double bond such as a vinyl monomer and then copolymerizing it with unsaturated carboxylic amide and the like. Japanese Patent Application Laid-Open Gazette No. 8-11421 discloses a technique of forming an ink absorbing material layer by a coating liquid obtained by mixing polyvinyl pyrrolidone, non-water-soluble acrylic resin, silica and organic minute particles with a solvent.
However, in the case of direct printing on the thermoplastic resin film, cloth, tarpaulin and the like by a water-base ink, such a film for printing is made of resin or fibers and therefore does not absorb the water-base ink but repels it. This makes it difficult to print a target image or pattern with a good definition. In particular, the water-base ink uses, as a solvent, water and a nonvolatile organic solvent (such as ethylene glycol, diethylene glycol and methyl carbitol), and such a solvent has a low drying speed. If multicolor printing is made with the use of such a solvent, at the printing of the second color after the printing of the first color, an ink of the first color is mixed with an ink of the second color so that bleeding readily occurs. This requires a long drying time, resulting in poor workability.
On the other hand, if printing is made on a laminated film obtained by providing the above-mentioned ink absorbing material layer on the base film, this increases printability. However, the laminated film cannot sufficiently obtain the definition of the images and the like, the dryability of the water-base ink and the fixativity of the water-base ink.